Oat Leaf Research Articles

FORMATION OF THE NUMBER OF PHYTOPATHOGENIC MICROMYCETE POPULATIONS IN AGROCENOSES OF OAT

The formation of the number of the phytopathogenic micromycete populations as a factor in biological pollution of oat agrocenoses is an important research field, the study of which will make it possible to create some sustainable agroecosystems. Therefore, the influence of the environmental factors (abiotic, biotic, anthropogenic, etc.) on the formation of micromycete populations on the vegetative organs of oat plants using different plant cultivation technologies was studied. This article presents the results of the ecological assessment of oat plant varieties based on the indicators of its their influence on the population number, the frequency of its occurrence, and the intensity of micromycete sporulation. Vegetative organs of oat plants of Parliamentsky and Tembre varieties were selected by BBCH scale for cereals in the phases: 5 tillers detectable (25), node 5 at least 2 cm above node 4 (35), еnd of heading: inflorescence fully emerged (39). It was determined that certain climatic conditions like an abiotic factor (namely an increase in air temperature), frequent droughts, or rare but abundant rains, significantly influenced the formation of micromycete populations in the oat leaf microbiome. Plant growing technologies, as an anthropogenic factor, influenced the spectrum of species and their frequency of the occurrence on the vegetative organs of oats of different kinds of the varieties. Using the organic technology of plant cultivation led to diversification of the spectrum of micromycete populations, but with a lower frequency of occurrence of species compared to the traditional technology of plant cultivation. Also, the varieties of oat plants, as a biotic factor, in terms of some physiological substances of plants, are able to restrain the spread of micromycete populations on the vegetative organs of plants or stimulate them. It was found out that using the traditional and organic technologies of plant cultivation on the vegetative organs of Tembre oat variety, the population density, the frequency of micromycete species occurrence, and the intensity of sporulation were significantly lower compared to the indexes of Parliamentsky oat variety plants. This points to the fact that the cultivation of oat varieties capable of resisting the formation of micromycete populations on an ecologically safe level will ensure a decrease in the level of biological pollution of agrocenoses and at the same time increase the biosafety of plant raw materials.

The formation of a phytopathogenic microbiome as a factor of biological pollution of agrocoenoses of vivas

The formation of the phytopathogenic microbiome as a factor in the biological contamination of oat agrocenoses is an important research task, the solution of which will make it possible to create ecologically balanced agroecosystems. This will increase their ability to self-regulate the population of micromycetes in order to obtain high-quality and safe oat raw materials. Therefore, the influence of environmental factors (abiotic, biotic, anthropogenic) on the formation of micromycete populations in the oat leaf microbiome under different plant growing technologies was studied. The article presents the results of ecological assessment of oat plant varieties based on indicators of influence on population density, frequency of occurrence, and intensity of sporulation of micromycetes. Vegetative organs of oat plants of Parlamentskyi and Tembr varieties were selected in the following phases: tillering, emergence into tubes and earing. It was determined that climatic conditions, as an abiotic factor, namely an increase in air temperature, frequent droughts, rare but abundant rains, which changed depending on the year of the study, significantly influenced the formation of micromycete populations in the oat leaf microbiome. Plant growing technologies, as an anthropogenic factor, significantly influenced the spectrum of species and their frequency of occurrence in the leaf microbiome of oats of various varieties. Under the organic technology of growing plants, the spectrum of micromycete populations was more diverse, but with a lower frequency of occurrence of species compared to the traditional technology of growing plants. Also, varieties of oat plants, as a biotic factor, thanks to the physiological substances of plants, are able to restrain the spread of micromycete populations in the leaf microbiome of plants or stimulate them. It was found out that with the traditional and organic technology of growing plants in the leaf microbiome of Tembr oat variety, the population density, the frequency of occurrence of micromycete species, and the intensity of sporulation were significantly lower compared to Parlamentskyi oat variety plants. This indicates that the cultivation of oat varieties capable of restraining the formation of micromycete populations at an ecologically safe level will ensure a decrease in the level of biological pollution of agrocenoses and increase the biosafety of plant raw materials

Community structure of endophytic fungi in roots and leaves of Fagopyrum mill and Avena sativa in a Chinese northern cold region

In order to explore the endophytic fungi of Fagopyrum Mill and Avena sativa, Illumina Miseq high-throughput sequencing was used to analyze the community structure and diversity of endophytic fungi in leaves and roots of buckwheat and oat at the mature stage. The results of community structure showed that there were 205 operational taxonomic units (OTUs) in buckwheat roots and 181 OTUs in buckwheat leaves based on 97% sequence similarity level. There were 152 OTUs and 127 OTUs in the root and the leaf of oat, respectively. At the phylum level, Ascomycota and Basidiomycota were the dominant endophytic fungi in buckwheat roots and leaves, while Ascomycota was the dominant endophytic fungus in oat roots and leaves. Alpha diversity analysis showed that the Ace index, Chao index and Shannon index of buckwheat roots were higher than that of buckwheat leaves, and the three indices of oat roots were also higher than that of oat leaves, indicating that the richness and diversity of endophytic fungi community in roots were higher than that in leaves. Biomarkers were found by significant difference analysis in buckwheat and oat. The endophytic functional groups of buckwheat and oat were mainly distributed in Pathotroph and Saprotroph. The results of this study laid a foundation for fully exploiting the dominant endophytic fungal resources of buckwheat and oat and further developing microbial fertilizers.

Incidence and Distribution of Barley yellow dwarf virus Infecting Oats in Korea

A survey of Barley yellow dwarf virus (BYDV) was conducted in major oat-growing areas of Korea in 2020. BYDV is an economically important pathogen of cereal crops that can be transmitted by aphids. The present study evaluated the genetic composition of BYDV in oat from eight geographical areas in Korea. Multiplex reverse transcription-polymerase chain reaction was used to screen 322 oat leaf samples for six BYDV strains (PAV, MAV, SGV, PAS, RPV, and RMV). The 125 samples (~39%) tested positive for BYDV. BYDV-PAV, BYDV-SGV, BYDV-PAS, and BYDV-RPV were detected from oat in different areas. Most of the BYDV-infected samples were assigned to subgroup I (n=112). The results indicate that BYDV-PAV could be dominant throughout Korea. Also, the phylogenetic analysis of coat protein sequences indicated that 23 BYDV isolates from Korea could be separated into two clades, which exhibited high nucleotide sequence similarity. In conclusion, the present survey provides a BYDV infection assessment for domestic oat varieties in Korea and basic information for the development of BYDV control measures in Korea’s oat industry.

Reverse Transcription Recombinase Polymerase Amplification Assay for Rapid and Sensitive Detection of Barley Yellow Dwarf Virus in Oat.

Barley yellow dwarf virus (BYDV) is an economically important plant pathogen that causes stunted growth, delayed heading, leaf yellowing, and purple leaf tip, thereby reducing the yields of cereal crops worldwide. In the present study, a reverse transcription recombinase polymerase amplification (RT-RPA) assay was developed for the detection of BYDV in oat leaf samples. The RT-RPA assay involved incubation at an isothermal temperature (42°C) and could be performed rapidly in 5 min. In addition, no cross-reactivity was observed to occur with other cereal-infecting viruses, and the method was 100 times more sensitive than conventional reverse transcription polymerase chain reaction. Furthermore, the assay was validated for the detection of BYDV in both field-collected oat leaves and viruliferous aphids. Thus, the RT-RPA assay developed in the present study represents a simple, rapid, sensitive, and reliable method for detecting BYDV in oats.

ИССЛЕДОВАНИЕ ОБРАЗОВАНИЯ БИОПЛЕНОК LISTERIA MONOCYTOGENES В РАСТЕНИЯХ И КОМБИКОРМАХ

The aim of the work is to study the biofilm formation of L. monocytogenes in plants and mixed fodder. Materials and methods. Oat seeds contaminated with antibiotics and washed from their residues were germinated. Oat seedlings were placed in the soil and grown for 10 days. The near-root zone was contaminated with Listeria suspension and morphology and biofilm formation of Listeria populations in vegetative organs of plants were studied after a certain period of time. Granulated feed was used as mixed fodder, exogenously contaminated with L. monocytogenes suspension. The morphological features of bacterial populations and the formation of biofilms were studied by scanning electron microscopy. Research results. Experimental bacteriological and morphological studies have shown that as a result of the contamination of the Listeria root zone, they penetrated through the capillary system of the roots into the oat leaf blades and were localized in chlorenchyma. In the studies by scanning electron microscopy of preparations obtained from the leaves, on the fragments of the inner part of the oat leaf (devoid of the epidermis), were identified cells with both a typical morphology and at various stages of heteromorphism, and the formation of biofilm was noted. In the study of mixed fodder by method SEM, it was shown that at low temperatures (4 ° C), during the first 24 hours, not only the adhesion of individual cells to the surfaces of the feed particles occurs, but also the formation of microcolonies and colonies often with the formation of biofilms, which indicates the active reproduction of these bacteria. At the same time, it was noted that at temperature of 37 ° C and an exposure of 24 hours, the processes of adhesion and cell colonization of Listeria particles of mixed fodder were slowed down under the same conditions, which seems to be due to the psychrophilicity of Listeria.

Validation of expression stability of reference genes in response to herbicide stress in wild oat (Avena ludoviciana)

Weeds are serious problem in crop production and wild oat is a grass weed of economic and agronomic significance. We need to extend our basic knowledge of weeds especially in molecular genetics and gene expression. For study of gene expression by semi-quantitative and quantitative PCR, it is recommended that normalization of reference genes be carried out in order to select the most stable reference gene for a precise gene expression study. The purpose of this research was evaluation of four reference genes in response to treated and untreated (control) by herbicide in two tissues (stem and leaf) of non-target site resistance wild oat (A. ludoviciana). Four candidate reference genes including Actin, Ef1α (elongation factor 1 alpha), GAPDH (glyceraldehyde 3-phosphate dehydrogenase) and TBP (TATA-box-binding protein) were used to determine stable reference gene exposed to the herbicide using the statistical methods of NormFinder, BestKeeper and delta-Ct. NormFinder indicated that TBP and Actin genes are the best combination of two genes for normalizing calculations (with a combined gene stability value of 0.012) for qPCR analysis under herbicide stress in different tissues of non-target site resistance wild oat. Based on the statistical results, the Ef1α gene was identified as the unstable reference gene. Totally, according to results of this study, TBP gene is the most stable reference gene and therefore, this gene can be used as a reference gene for future studies of quantitative PCR analysis of herbicide stress-responsive gene expression in wild oat and potentially in other grass weed species.

Terminação de novilhos em pastagem de aveia branca consorciada com leguminosa ou associada à suplementação energética

O objetivo do experimento foi avaliar a associação da ervilhaca (Vica sativa) ou da suplementação energética em pastagem de aveia branca (Avena sativa) sobre o desempenho de novilhos de corte na fase de terminação. Foram utilizados 18 novilhos castrados, 1/4 Marchegiana 1/4Aberdeen Angus2/4 Nelore, com peso vivo e idade média de 360kg e 19 meses, respectivamente, divididos em três tratamentos: pastagem de aveia branca, pastagem de aveia branca consorciada com ervilhaca e pastagem de aveia branca com suplementação energética (milho grão triturado, 1% do peso vivo por dia, na matéria seca). O delineamento experimental utilizado foi o de blocos ao acaso com três tratamentos e três repetições. Houve interação significativa entre o período de avaliação e os tratamentos para participação do componente folha da aveia na pastagem. A participação da ervilhaca aumentou no decorrer do experimento de 3,51% para 12,21% consequentemente a participação da aveia diminuiu no decorrer do experimento. Não houve diferença significativa (P>0,05) para massa de forragem, carga animal, oferta de forragem e taxa de acúmulo diário entre os tratamentos. Os animais que receberam suplementação apresentaram maior (P<0,05) ganho de peso médio diário (1,08kg/dia), ganho de peso vivo por hectare (4,47kg/ha/dia) e ganho de peso vivo total (242,82kg) em comparação com aqueles que receberam somente a pastagem de aveia (0,68kg; 2,50kg/ha/dia; 123,49kg, respectivamente). Já os animais que permaneceram em pastagem consorciada de aveia e ervilhaca apresentaram resultados intermediários (0,89kg/dia; 2,99kg/ha/dia e 154,26kg, respectivamente). O melhor peso final foi para o tratamento com suplementação (424,44kg). A suplementação energética em pastagem de aveia branca apresentou melhores resultados de desempenho animal. No entanto, a consorciação de aveia branca e ervilhaca é uma alternativa quando o suplemento (grão de milho) está com um custo elevado, uma vez que o desempenho, apesar de menor, não foi diferente dos animais suplementados.

Effect of Simulated Radiation on Sethoxydim Performance Used with and without Vegetable Oils

The photodecomposition of post emergence herbicides on leaf surface can be affected via adding vegetable oils to spray tank. Nine vegetable oils were compared to assess the photodecomposition of sethoxydim on wild oat leaf surface under simulated light conditions. The experiment was conducted as completely randomized factorial design with three replications at the College of Agriculture, Ferdowsi University of Mashhad, Iran, in 2013. Each herbicidal solution (with and without vegetable oil) was exposed to simulated light at 0, 5, 10, 20, 30, 60, 120 and 240 MAS (min after spray), for 30 min. The performance of sethoxydim in the presence of turnip, olive, soybean, corn, sunflower, canola, sesame, castor and cotton seed oils, compared to non-vegetable oil solution, increased up to 4.02-, 3.44-, 3.22-, 3.08-, 2.86-, 2.09-, 1.96-, 1.77- and 1.25- fold. All vegetable oils significantly improved the resistance of sethoxydim to light treatment. The effect of vegetable oils on the resistance to photodecomposition of sethoxydim was significant different at less than 60 MAS, while no significant differences were noted among vegetable oils when light treatment occurred at 120 and 240 MAS. Data from the light treatments have confirmed that when vegetable oils were added to sethoxydim, light adverse effect was lower, which is presumably due to disturbance of the cuticule and the rapid absorption of sethoxydim by wild oat leaves. Vegetable oils fatty acids composition effect the resistance to photodecomposition of sethoxydim, as with increasing the unsaturated fatty acid values, the resistance to photodecomposition was improved.

Effect of Simulated Radiation on Sethoxydim Performance Used with and without Vegetable Oils

The photodecomposition of post emergence herbicides on leaf surface can be affected via adding vegetable oils to spray tank. Nine vegetable oils were compared to assess the photodecomposition of sethoxydim on wild oat leaf surface under simulated light conditions. The experiment was conducted as completely randomized factorial design with three replications at the College of Agriculture, Ferdowsi University of Mashhad, Iran, in 2013. Each herbicidal solution (with and without vegetable oil) was exposed to simulated light at 0, 5, 10, 20, 30, 60, 120 and 240 MAS (min after spray), for 30 min. The performance of sethoxydim in the presence of turnip, olive, soybean, corn, sunflower, canola, sesame, castor and cotton seed oils, compared to non-vegetable oil solution, increased up to 4.02-, 3.44-, 3.22-, 3.08-, 2.86-, 2.09-, 1.96-, 1.77- and 1.25- fold. All vegetable oils significantly improved the resistance of sethoxydim to light treatment. The effect of vegetable oils on the resistance to photodecomposition of sethoxydim was significant different at less than 60 MAS, while no significant differences were noted among vegetable oils when light treatment occurred at 120 and 240 MAS. Data from the light treatments have confirmed that when vegetable oils were added to sethoxydim, light adverse effect was lower, which is presumably due to disturbance of the cuticule and the rapid absorption of sethoxydim by wild oat leaves. Vegetable oils fatty acids composition effect the resistance to photodecomposition of sethoxydim, as with increasing the unsaturated fatty acid values, the resistance to photodecomposition was improved.

Changes in metabolism of cell wall polysaccharides in oat leaves during senescence: relevance to the senescence-promoting effect of methyl jasmonate

Changes in cell wall polysaccharides in oat (Avena sativa L.) leaf segments during senescence promoted by methyl jasmonate (JA-Me) were studied. During the incubation with water at 25 °C in the dark, the loss of chlorophyll of the segments excised from the primary leaves of 8-day-old green seedlings was found dramatically just after leaf excision, and leaf color completely turned to yellow after the 3- to 4-day incubation in the dark. Application of 10 µM JA-Me substantially promoted the loss of chlorophyll corresponding with the chloroplast degradation. Cell wall polysaccharides in oat leaf segments mainly consisted of hemicellulosic and cellulosic ones. During the process of leaf senescence, the amount of hemicellulosic I and II, and cellulosic polysaccharides decreased, but little in pectic polysaccharides. JA-Me significantly enhanced the decrease in cellulosic polysaccharides, but little in hemicellulosic ones. Arabinose, xylose and glucose were identified as main constituents of neutral sugars of hemicellulosic polysaccharides. The neutral sugar compositions of hemicellulosic polysaccharides changed little during leaf senescence both in the presence or absence of JA-Me. These facts suggest that JA-Me affects sugar metabolism relating to cellulosic polysaccharides during leaf senescence.

Production parameters and forage loss of oat and rye grass pastures managed with beef heifers fed diets with energy supplementation

Production parameters of intercropped pastures of oat and rye grass managed with beef heifers supplemented with brown rice meal and/or protected fat were evaluated. Twenty-eight Charolais × Nellore crossbred heifers at initial average age of 18 months and initial average live weight of 274.9 kg were utilized in the experiment. Animals were kept on oat + rye grass pastures and distributed in the following treatments: no-supplementation (NS): heifers kept only in pastures; Megalac (MEG): supplementation with protected fat; brown rice meal (BRM): supplementation with BRM; BRM + MEG: supplementation with BRM plus protected fat. The greater participation of oat leaf was from July 5th to August 10th, 2009 and of rye grass, from August 30th to September 26th, 2009. The crude protein content increased until the 55th day (225.1 g/kg). Pasture total digestible nutrients presented a cubic behavior, with an average of 722.0 g/kg. The highest supply of leaf blades, 5.17 kg of dry matter/100 kg of live weight, was found in the second period. Pasture intake increased throughout the periods. Forage mass and support capacity of the animal did not differ between treatments, presenting means of 1245.02 kg of dry matter/ha and 882 kg of live weight/ha, respectively. Stoking rate, forage loss and pasture intake were not affected by the treatments. Supplementation of beef heifers with rice meal and/or protected fat did not change production parameters of oat + rye grass pastures or pasture intake. Increase in daily accumulation rate of dry matter and supporting capacity of the animals increases forage losses.

Individual Maize Chromosomes in the C3 Plant Oat Can Increase Bundle Sheath Cell Size and Vein Density

C(4) photosynthesis has evolved in at least 66 lineages within the angiosperms and involves alterations to the biochemistry, cell biology, and development of leaves. The characteristic "Kranz" anatomy of most C(4) leaves was discovered in the 1890s, but the genetic basis of these traits remains poorly defined. Oat × maize addition lines allow the effects of individual maize (Zea mays; C(4)) chromosomes to be investigated in an oat (Avena sativa; C(3)) genetic background. Here, we have determined the extent to which maize chromosomes can introduce C(4) characteristics into oat and have associated any C(4)-like changes with specific maize chromosomes. While there is no indication of a simultaneous change to C(4) biochemistry, leaf anatomy, and ultrastructure in any of the oat × maize addition lines, the C(3) oat leaf can be modified at multiple levels. Maize genes encoding phosphoenolpyruvate carboxylase, pyruvate, orthophosphate dikinase, and the 2'-oxoglutarate/malate transporter are expressed in oat and generate transcripts of the correct size. Three maize chromosomes independently cause increases in vein density, and maize chromosome 3 results in larger bundle sheath cells with increased cell wall lipid deposition in oat leaves. These data provide proof of principle that aspects of C(4) biology could be integrated into leaves of C(3) crops.

Aluminium content in leaf and root of oat (Avena sativa L.) grown on pseudogley soil

Acid soils are not suitable for cultivation of agricultural crops as increased concentrations of hydrogen ions hinder the uptake of most nutrients. The adverse effects of increased soil acidity also include release of aluminium (Al) ions from the adsorption complex and hence, an increase in their concentration in the soil solution and plants. Aluminium ions block phosphorus and potassium uptake by the crop, thus leading to disturbance of plant growth and development, as well as to a substantial decline in crop yield and quality. This suggests that the use of such soils is not justified in terms of successful plant production. The objective of this study was to use liming to neutralise excess acidity of pseudogley soil under oat crop and evaluate the effect of soil pH improvement measures on the aluminium content of both the leaf and root of oat ( Avena sativa L.) cv. Mediteran. Three liming treatments were employed [1.0, 3.0 and 4.0 t ha -1 calcium carbonate (CaCO 3 )]. The treatments with 3.0 and 4.0 t ha -1 CaCO 3 induced no Al presence in oat plants, suggesting that liming in these treatments was successful in terms of aluminium content. Key words: Aluminium, leaf, oat, pseudogley, root.

Light qualities and dose influence ascorbate pool size in detached oat leaves

In this work, we studied the mechanism of light influence on AsA pool size in Avena sativa L. under the effects of low intensity light at different wavelengths. Exposure to low intensity light of oat leaf segments incubated in water or in l-galactono-1,4-lactone (GL), resulted in an increase in AsA content compared with the dark control. This increase was due to modulation of l-galactono-1,4-lactone dehydrogenase (GLDH; EC 1.3.2.3) light-dependent activity and was dependent on the size of the endogenous GL pool. Both blue and red light were effective in increasing AsA, and this increase depended on both exposure time and light intensity. Protein biosynthesis, photosynthesis and calcium were involved in controlling the level of light-dependent AsA. We suggest that multiple checkpoints correlated to the presence of light underlie the ascorbate pool size. The presence of a light-activated switch for the maintenance of an adequate AsA level seems to be necessary for the various tasks of scavenging reactive oxygen species, in response to the dark-light cycle which plants experience under natural conditions.

Induction of Chlorosis, ROS Generation and Cell Death by a Toxin Isolated fromPyricularia oryzae

The ethyl acetate extract of the conidia germination fluid from an Avena isolate (Br58) of Pyricularia oryzae had chlorosis-inducing activity on oat leaf segments. The same activity was also present in the acetone extract of an oatmeal agar culture of Br58. Fungal cultures were used for a large-scale preparation. A series of acetone and ethyl acetate extraction monitored by chromatography was used to isolate an active fraction. The active principle was purified by HPLC. We show by NMR and LC/MS that the toxin was an oxidized C18 unsaturated fatty acid named Mag-toxin. Mag-toxin induced chlorosis on oat leaf segments incubated in the light but not in the dark. Reactive oxygen species (ROS) and cell death were induced by Mag-toxin in oat cells. The sub-cellular localization of ROS generation induced by the toxin treatment was correlated with the location of mitochondria. Interestingly, the induction of ROS generation and cell death by Mag-toxin was light-independent.

Modelos de pontos críticos para relacionar o rendimento de grãos de aveia branca com a intensidade de doença no patossistema múltiplo ferrugem da folha: helmintosporiose

A ferrugem da folha e a helmintosporiose são as principais doenças fúngicas foliares de aveia branca. Em cultivares suscetíveis, o controle químico não considera o limiar de dano econômico (LDE). O objetivo deste trabalho foi obter funções de dano, por modelos de ponto crítico, ao relacionar o dano pela ocorrência simultânea da ferrugem da folha e a helmintosporiose com o rendimento de grãos nas safras de 2006 e 2007, em Lages, Santa Catarina (SC). O gradiente da intensidade das doenças foi gerado por número de aplicações e doses de fungicidas nas cultivares 'UPFA 20' e 'UPFA 22'. Os ensaios consistiram de 10 tratamentos, distribuídos em blocos casualizados, com quatro repetições. As doenças foram avaliadas nos estádios de alongamento, emborrachamento e florescimento. Os modelos de ponto crítico foram obtidos por regressão linear entre rendimento de grãos e incidência (I) e severidade (S). Em 2006, funções significativas foram obtidas para 'UPFA 20' no emborrachamento (R=6.345-22,07I), enquanto para a 'UPFA 22' foi obtida no alongamento (R=5.726-17,96I; R=5.160-541,5S), emborrachamento (R=5.961-21,85I; R=5.433-966,8S) e florescimento (R=6.217-36,41I; R=5.539-1.185S). Em 2007, para 'UPFA 20', no alongamento (R=6.369-55,61I; R=4.965-2.911S), emborrachamento (R=6.620-40,91I; R=5.181-1.702S) e florescimento (R=6.129-32,34I; R=5.252-638,6S), e para 'UPFA 22', no alongamento (R=5.201-41,96I; R=4.977-657,8S), emborrachamento (R=5.329-60,51I; R=4.238-798,1S) e florescimento (R=5.604-32,83I; R=4.680-588,5S). A produção na cultivar 'UPFA 22' foi mais afetada pela ocorrência das doenças, e a intensidade das doenças no estádio de florescimento apresentou maior relação com o rendimento de grãos. As funções geradas permitem obter o coeficiente de dano para uso no cálculo do LDE em patossistema múltiplo ferrugem da folha e helmintosporiose.

Biosynthesis of avenanthramides in suspension cultures of oat (Avena sativa)

Oats produce a group of secondary metabolites termed avenanthramides (avn). These compounds are biosynthesized through the action of the enzyme hydroxycinnamoyl CoA: hydroxyanthranilate N-hydroxycinnamoyl transferase (HHT) which catalyzes the condensation of one of several cinnamate CoA thioesters with the amine functionality of anthranilic acid, 4-hydroxy- or 5-hydroxy-anthranilic acid. In oat leaf tissue the biosynthesis of avenanthramides appears to result from elicitation by fungal infection. Here we demonstrate the biosynthesis of several avenanthramides in suspension cultures of oat apical meristem callus tissue. This phenomenon appears as a generalized pathogen response, evidenced by the production of PR-1 mRNA, in response to elicitation with chitin (poly-N-acetyl glucosamine). The suspension cultures also produce relatively large quantities of avnA and G in response to chitin elicitation. Under certain culture conditions avnB and C are also produced as well as three additional metabolites tentatively identified as avnH, O and R. These findings portend the utility of oat suspension culture as a tool for more detailed investigation of the mechanisms triggering their biosynthesis as well as the factors dictating the particular types of avenanthramides biosynthesized.

Detached-Leaf Method for Propagating Puccinia coronata and Assessing Crown Rust Resistance in Oat.

The crown rust pathogen Puccinia coronata is an obligate biotroph with wind-disseminated propagules and numerous races. These characteristics make propagation of single-race cultures difficult. Genetic studies using single races in field and greenhouse environments are also problematic because pure cultures can easily become contaminated. In this study, we developed an isolated propagation system for P. coronata and tested its ability to assess host resistance. Oat (Avena sativa) leaf sections (10 cm each) were harvested, disinfested, and suspended in sterile plastic boxes by enclosing 3.5-cm linear sections of each leaf end between 4% agar blocks amended with various chemical constituents. The exposed sections (approximately 3 cm) were inoculated with P. coronata urediniospores suspended in water. Boxes were sealed and incubated in a lighted growth cabinet until the pathogen sporulated. Viable spores were produced on leaves in all treatments, whereas 6-benzylaminopurine (BAP) and kinetin treatments sustained the leaves longer and yielded the most viable spores. Based on these data, the BAP treatment was adopted and used for additional studies. Detached leaves of differential oat cultivars produced the same reactions as whole plants screened under standard conditions in a growth chamber. The proposed detached-leaf system should be useful for the propagation of numerous single-race cultures of P. coronata as well as evaluation of host resistance under highly controlled conditions.

Componentes morfológicos e produção de forragem de pastagem de aveia e azevém manejada em diferentes alturas

Avaliou-se a dinâmica de produção de forragem em pastagem de aveia-preta (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam) manejada em diversas alturas de manejo com o objetivo de evidenciar as potencialidades dessa mistura em sistemas de integração lavoura-pecuária. Os tratamentos consistiram de quatro alturas de manejo da pastagem (10; 20; 30 e 40 cm), medidas com bastão graduado e avaliadas em blocos casualizados com três repetições. O método de pastejo foi contínuo, com taxa de lotação variável. Utilizaram-se bezerros de corte mestiços com 10 meses de idade e peso médio inicial de 210 kg, respectivamente. As características da pastagem estudadas foram: massa de forragem (MF); taxa de acúmulo de forragem (TAC); produção total de forragem (PTMS); e quantificação dos componentes morfológicos da pastagem (colmo, lâmina e material morto). A massa de forragem aumentou de forma linear de acordo com a altura do pasto, uma vez que, para cada cm de aumento na altura superior a 10 cm, a matéria seca aumentou aproximadamente 90 kg/ha. Não houve efeito das alturas da pastagem sobre a TAC ou sobre a PTMS, cujos valores médios foram de 66,8 kg/ha/dia de MS e 10.721 kg/ha de MS, respectivamente. A porcentagem de folhas de azevém foi maior que a de folhas de aveia nos três períodos de avaliação e, na altura de 10 cm, foi superior à obtida nas demais alturas na última avaliação (em torno de 20% da participação total da massa de forragem). A aveia apresenta rápido desenvolvimento inicial e diminuição na produção nos períodos posteriores de desenvolvimento.